Understanding Powder Metallurgy: This Article Explains It All

Powder metallurgy is a process technology that produces metal materials, composite materials, and various types of products by forming and sintering using metal powder (or a mixture of metal powder and non-metal powder) as raw materials. Broadly, the powder metallurgy products industry includes iron and steel tools, hard alloys, magnetic materials, and powder metallurgy products. Narrowly, it only refers to powder metallurgy products, including powder metallurgy parts (which account for the majority), oil-impregnated bearings, and metal injection molded products. Today we will take a detailed look at this process.

Powder Metallurgy Process Characteristics

Controllable density of products, such as porous materials and good density materials;

Fine grain, uniform microstructure, no composition segregation;

Near-net shaping with raw material utilization rate > 95%;

Less or no cutting, with cutting processing only at 40~50%;

Controllable material components, beneficial for preparing composite materials;

Preparation of hard-to-melt metals, ceramic materials, and nuclear materials.

Powder Metallurgy Basic Process Flow

Powder Preparation

The process of making powder from raw materials. Common methods include oxide reduction and mechanical processes.

Mixing

Mixing various required powders in a certain proportion and homogenizing them to form a blend. There are dry, semi-dry, and wet methods, used for different requirements.

Forming

Forming is the process of pressing the mixed and homogenized blend into a mold to create a green compact with a certain shape, size, and density. Forming methods are basically divided into pressure forming and non-pressure forming, with mold pressing being the most commonly used in pressure forming.

Sintering

Sintering is the process of heating the green compact at high temperature to cause diffusion and bonding between particles, eventually forming a dense solid material. The sintering temperature and time need to be precisely controlled based on the material's properties and requirements. The sintering process can be divided into solid-phase sintering and liquid-phase sintering. Solid-phase sintering is carried out without the appearance of a liquid phase, whereas liquid-phase sintering happens with partial material melting.

Post-processing

Post-processing involves further machining and treatment of the sintered products to meet the final application requirements. Common post-processing methods include mechanical processing, heat treatment, and surface treatment. Mechanical processing can improve the dimensional accuracy and surface quality of the product, heat treatment can enhance the mechanical properties of the material, and surface treatment can increase the product's corrosion resistance and aesthetics.

Quality Inspection

Quality inspection involves testing and evaluating powder metallurgy products to ensure they meet design and usage requirements. Common inspection methods include dimensional measurement, microstructure observation, mechanical properties testing, and chemical composition analysis. Through quality inspection, issues in the production process can be identified and corrected, ensuring product quality and reliability.

Powder Metallurgy Application Fields

The powder metallurgy process has a wide range of application fields, mainly including the following aspects:

Automotive Industry: Powder metallurgy parts are widely used in automotive engines, transmissions, chassis, and other components, such as gears, bearings, and connecting rods.

Aerospace: Powder metallurgy materials and products have important applications in aerospace, such as high-temperature alloys, titanium alloys, and composite materials.

Electronics and Electrical Appliances: Powder metallurgy processes are used to manufacture various electronic components and electrical parts, such as magnetic materials, contact materials, and heat sinks.

Tool Manufacturing: Powder metallurgy is used to produce various high-performance tools, such as hard alloy tools, molds, and abrasives.

Medical Devices: Powder metallurgy processes are used to make various medical devices and implants, such as artificial joints, dental materials, and orthopedic implants.

Energy Industry: Powder metallurgy processes are used to manufacture various energy equipment and components, such as fuel cells, battery electrodes, and nuclear materials.

In summary, due to its unique advantages and broad application prospects, powder metallurgy has become an essential technology in modern manufacturing. With continuous technological progress and development, powder metallurgy will play an even greater role in more fields.